Production of textile materials with improved flame retardance

ABSTRACT

THE FLAME RETARDANT PROPERTIES OF TEXTILE MATERIALS WHICH HAVE BEEN REACTED WITH PHOSPHORUS-CONTAINING COMPOUNDS OR SALTS THEREOF, ARE IMPROVED BY AN AFTER-TREATMENT OF THE TEXTILE MATERIAL WITH A SALT OF A HEAVY METAL, FOR EXAMPLE, TITANIUM TETRACHLORIDE. THE TREATMENT NOT ONLY IMPARTS INCREASED FLAME RETARDANCE TO TREATED TEXTILE MATERIALS BUT PROTECTS THE IMPARTED FLAME RETARDANCE AGAINST SUBSEQUENT IMPAIRMENT BY ION EXCHANGE WITH CALCIUM AND OTHER ELEMENTS IN WATER. CONSEQUENTLY, THE TREATMENT EXTENDS THE EFFECTIVE LIFE OF FLAME RETARDANCE OVER A LARGE NUMBER OF LAUNDERINGS. THE TREATMENT IS APPLICABLE TO CELLULOSIC FIBERS, E.G., COTTON OR RAYON, AS WELL AS TO WOOL, SILK AND OTHER NATURAL AND MAN-MADE FIBERS.

United States Patent C) 3,827,907 PRODUCTION OF TEXTILE MATERIALS WITHIMPROVED FLAME RETARDANCE Robert Bruce LeBlanc, Wickford, R.I., assignorto Cotton, Incorporated, New York, N.Y.

No Drawing. Continuation-impart of abandoned application Ser. No.220,453, Jan. 24, 1972. This application Nov. 20, 1972 ,Ser. No. 307,796

Int. Cl. B44d N44 US. Cl. 11762.1 16 Claims ABSTRACT OF THE DISCLOSUREThe flame retardant properties of textile materials WhlCh have beenreacted with phosphorus-containing compounds or salts thereof, areimproved by an after-treatment of the textile material with a salt of aheavy metal, for ex ample, titanium tetrachloride. The treatment notonly imparts increased flame retardance to treated textile materials butprotects the imparted flame retardance against subsequent impairment byion exchange with calcium and other elements in water. Consequently, thetreatment extends the eifective life of flame retardance over a largenumber of launderings. The treatment is applicable to cellulosic fibers,e.g., cotton or rayon, as well as to wool, silk and other natural andman-made fibers.

RELATED APPLICATION This application is a continuation-in-part of Ser.No. 220,453, filed Jan. 24, 1972 and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a novelmethod for imparting improved flame retardance to textile materialswhich have been treated with flame retardant phosphoruscontainingcompounds, and for improving the durability of such flame retardanceduring laundering.

It has become a widely accepted practice in the textile industry totreat textile materials, especially cellulosic materials such as cottonor rayon, but also wool, silk and various synthetic fibers, for thepurpose of rendering the material resistant to the action of flame andheat. Such practice has assumed increasing importance with the adoptionof legislation designed to protect the public against the hazards ofinflammable fabrics in articles of clothing, toys, household articlessuch as curtains and drapes, and the like.

'A broadgroup of flameproofing agents or flame retardants which havereceived extensive attention is represented by the inorganic and theorganic phosphorus compounds. One theory to explain why such phosphoruscompounds function as flame retardants for substrates, especially organcsubstrates such as cellulose, is that they produce phosphorus pentoxideduring exposure to flame. The liberated P which is a Lewis acid,thereupon acts on the organic fiber substrate to dehydrate it, making itless flammable. Another theory is that the phosphorus compounds changethe path of degradation to prevent the formation of levoglucosan, toincrease the amount of carbon, water and carbon dioxide and to reducethe amount of flammable, volatile gases and flammable tars. Examples ofagents which have been employed in the priorart for this purpose includesalts oforthophosphoric acid and other acids of phosphorus, such asdiammonium phosphate, and salts formed from mixtures of an aliphaticorganic base and an acid of phosphorus. The acids of phosphorus whichhave been used to form salts with or ganic bases include, for example,orthophosphoric acid, phosphorous acid, pyrophosphoric acid, and methylphosphonic acid. Typical organic bases include cyanamide and urea. Thesesalts may be employed per se, or in association with haloalkylphosphonic acid derivatives and phosphate esters, which are alsoflameproofing agents.

Another type of phosphorus-containing flameproofing agents comprises thehaloal kylphosphonic acids and their salts, such aschloromethylphosphonic acid. These compounds react with a portion of thehydroxyl groups of the cellulose or other hydroxyl-containing fibermolecule, thereby forming ethers and chemically modifying the textilematerial by incorporating phosphorus into the fibers.

One of the drawbacks of such phosphorus-containing flame retardants hasbeen their ability to undergo ion exchange when the textile material islaundered in water containing alkali metal or alkaline earth metalcompounds which causes a loss of fire retardance. Thus, textiles can berendered fire retardant by the application of a compound such asdiammonium phosphate to form a monophosphate ester of cellulose,CellOP(O)(OH) or an ammonium salt thereof. However, this fire retardancecan be lost in a single laundering in water containing even smallamounts of alkali metal or alkaline earth metal compounds, because ofthe conversion of this readily decomposable monophosphate ester orammonium salt into an alkali metal or alkaline earth metal salt whichdoes not decompose readily into P 0 when heated.

These ion exchange properties are exhibited by a number of phosphorusflame retardants. The phosphorus can be in a compound linked chemicallyto the cellulose or in a compound which is deposited as an insolubledeposit in or on the textile fibers. The groups which are usuallyassociated in ion exchange properties are acidic OH groups. But ionexchange can take place with other groups which are capable of linkingwith metal ions such as alkali metal and alkaline earth metal ions. Thegroups can be attached to the phosphorus atoms or attached to otheratoms which are on the textile.

Normally the metal ions that cause the most trouble during lanuderingare the so-called hard water ions such as calcium and magnesium. We willrefer to hard water ions as being the ones causing loss of fireretardance, but it is to be understood that both the usual hard waterions and ions such as sodium and potassium can be ion exchanged by thefire retardant fabric with subsequent loss of fire retardance. Theprocess of this invention protects the fabric not only from hard waterions, but also all of the alkali metal and alkaline earth metal ions.

No matter what the mechanism of the ion exchange, the eifect on the fireretardance of the textile laundered in hard water is the same: a loss offire retardance associated with a pick-up of hard water ions. This istheoretically due to these metals such as calcium tieing up phosphorusduring the combustion process so that the phos phorus may not functionas a flame retardant.

Thus, for example, it is known that cellulose can be phosphonomethylatedby treatment with the sodium salt of chloromethylphosphonic acid inaccordance with the equation:

C1CH P(O) (ONa) +CellOH+NaOH- CellOCH P (O) (ONa +NaCl.

When the treated textile is acidified with an acid such as hydrochloricacid, the sodium salt is transformed into the acid from aphosphonomethylated cellulose which has two free acid groups on thephosphorus atom. Whether it is in the salt form or in the free acidform, it is capable of picking up calcium ionsby ion exchange when it islaundered in' hard water,"forming a calcium phosphonate salt which doesnot readily'decompose.

A similar tendency toward ion exchange with calcium and other ions inhard water is found in textiles'treated with salts of organic basesandphosphoricacid, which present some acid groups for ion exchange.

It has been proposed (see US. Pat. 2,728,680) to apply a mixed solutionof a soluble chloride of tetravalent titanium and a soluble inorganicphosphate to cellulosic material as a flame retardant. The mixture isgelatinized and adhered onto the fabric. The solutions, however, onlycontain a small amount of phosphorus (0.02 to 0.17 part of phosphorusper part of titanium) and attempts to add higher proportions ofphosphorus to such titanium tetrachloride solutions result inprecipitation of titanium phosphate. The addition to the solution ofantimony trichloride, another known flame retardant agent, is thusrecommended in the patent to improve the fire-resistant properties ofthe treated fabric, particularly after laundering.

GENERAL DESCRIPTION OF THE INVENTION In accordance with the presentinvention there is provided a novel method whereby the durability offlame retardant properties of textile materials treated withphosphorus-containing agents aflixed to the material in an amount offrom about 0.5 to about 5 percent of phosphorus based on the weight ofthe material is improved by the after-treatment of the textile materialwith a salt of a heavy metal or a transition metal, i.e., a metal whichis in Group I-B or in a Group higher than Group III of the PeriodicTable of Elements. If a metal can exist in different valence states,salts wherein the metal is in a higher valence state are usually moreeffective for the purposes of the present invention than the same metalsin a lower valence state.

The treatment of the invention serves to increase the flameproofingeffect of the flameproofing agent and protect it against ion exchange orother effects of exposure to hard water, thereby promoting flameresistance and increasing its retention over a large number oflaunderings.

The materials or substrates to which the invention is applicable includetextiles or webs formed of cotton and other cellulosic fibers such aslinen, regenerated cellulose, viscose rayon, and partially etherified oresterified cellulosic materials; other forms of cellulose such as paperor wood products; proteinaceous textiles, such as wool, silk, or fibermade from casein; as well as textile blends containing one or several ofthe foregoing fiber types. The textile materials may be in the form offibers, yarns, fabrics (woven, non-woven or knitted), webbing and so on.The invention is particularly useful with textile materials having afabric weight of about 5 or more ounces per square yard.

The practice of the invention will be illustrated with regard to cottontextiles, but it is to be understood that this is for purposes ofillustration, and is not to be regarded as limiting.

The invention is especially applicable in conjunction with organic orinorganic phosphorus compounds which are applied to the textile materialor other substrate by impregnation and chemical modification and whichcontain groups such as acid or hydroxy groups, that is, groups which arecapable of undergoing ion exchange either in the free acid form or thesalt form such as the ammonium or alkali metal salt. Examples of usefulinorganic phosphorus compounds include phosphoric acid, H PO its saltssuch as diammonium phosphate, as well as combinations of phosphoric acidwith organic bases such as urea, cyanamide or dicyandiamide.

However, the invention is also applicable to cellulose or othersubstrate which is reacted with a phosphorus compound such as ahaloalkyl phosphonic acid derivative, e.g., chloromethylphosphonic acid,to the extent that the resulting product is capable of undergoingfurther reaction with a transition metal compound, for example, titaniumtetrachloride, ferric sulfate, or ammonium molybdate.

Regardless, the substrate is suitably treated to provide a phosphoruscontent on the substrate from about 0.5 to

about 5, preferably from about 0.8 to about 3, percent by weight of thesubstrate.

The metals whose compounds may be employed to react with thephosphorus-containing flame retardants or with textiles incorporatingsuch retardants generally are those which are bracketed under theheading Heavy Metals in the Periodic Chart of Elements, and particularlythose heavy metals which fall in Groups I-B, *IV-A, IV-B, V-A, V-B,VI-B, VII-B and VIII of the Chart. As different arrangements of thePeriodic Chart of the Elements are known in the art, when the termsPeriodic Chart of the Elements, Periodic Chart or Periodic Table areused in this specification, these terms shall be understood to refer tothe particular arrangement which is shown at pages 5657, Langes Handbookof Chemistry, Ninth Edition, Handbook Publishers, Inc., Sandusky, Ohio(1956).

More specifically, representative heavy metals whose compounds may beused include copper (I-B), tin (IV- A), lead (IV-A), titanium (IV-B),arsenic (V-A), antimony (V-A), bismuth (V-A), chromium (VI-B),molybdenum (VI-B), tungsten (VI-B), manganese (VII-B), iron (VIII),cobalt (VIII), nickel (VIII), thorium (actinide series), and so on.Salts of titanium are particularly preferred when it is desired to makewhite or light colored products. However, compounds of other metals arealso useful when product color is unimportant or when the saltcontributes a color which is actually desired. Thus, for instance,copper and iron salts may sometimes be preferred either because of theirrelatively low cost or because of the colors or other effects which theyproduce. In conjunction with chromium they may be used as dyeing, mildewproofing, fire retardant combination finishes. Mixtures of heavy metalsare also contemplated although in some cases mixtures of heavy metalssuitable when used singly may not be as suitable. The efficacy of aparticular mixture may be readily determined by a preliminary, empiricalscreening test.

The metal in its compounds may be in the cation, as in titaniumtetrachloride, or the anion, as in ammonium molybdate. When the metal isthe cation, the compound may be a salt or a basic salt such as achloride, bromide, iodide, fluoride, sulfate, nitrate, or acetate.Examples of other suitable salts include titanium chloride acetate,titanium acetate, titanium sulfate, titanium tetrabromide, titanylsulfate, chromic chloride, zirconium acetate, ferric sulfate, cupricchloride, stannic chloride, antimony trichloride, thorium tetrabromide,thorium tetrachloride and tungsten tetrachloride. Examples of suitablesalts wherein the heavy metal is present in the anion include, forexample, ammonium molybdate and sodium molybdate.

In the case of titanium tetrachloride, it has been found especiallyadvantageous to add to it two moles of an alkali metal base, NaOH,making the product TiCl OH) a basic salt. In comparison to a stronglyacid salt such as TiCl the basic salt such as TiCl (OH) tends to resultin better strength retention in the treated substrate. TiCl OH andTiCl(OH) are other forms of titanium chloride hydroxide which areuseful.

The metal compounds or salts can be applied to the pretreatedflameproofed textile substrates from any suitable solvent which does notdissolve or otherwise undesirably attack the substrate and in which theparticular compound used is soluble. Because of economic reasons andalso because of its beneficial swelling effect on substrates such ascellulose, water is usually the preferred solvent in the case of metalcompounds which are water soluble, but other solvents such as alcoholsare also usable.

The quantity of heavy metal which is desirably applied to the phosphoruspretreated textile substrate is that which is effective in permittingenough of the heavy metal ions to become attached to the ion exchangesites of the flameproofing compound such that there are not sufficiention exchange sites left unoccupied to cause a loss in fire rea tardanceby picking up calcium during laundering. In practice, such an effectivequantity of the heavy metal is readily determined in each case by alimited number of preliminary, empirical screening tests.

As a more quantitative guideline it may be suggested that in a systemusing a phosphorus compound having two OH groups as the flameproofingagent and a salt such as TiCL; or TiCl (OH) as the heavy metal salt, theflameproofing agent. will be capable of picking up about one atom of ametal such as titanium per atom of phosphorus.-Acco'rdingly,' in such acase it is preferred to apply the titanium salt solution to thepretreated textile in a proportion producing an atomic ratio of about1:1 for Ti to P in the treated textile. However, a satisfactory finishmay generally be obtained when the Ti/ P atomic ratio is in the rangefrom'0.5:1 to 5:1, preferably from 0.75 :1 to3:l.

Naturally, there is a certain tolerance or range within which thetextile material can pick up alkali metal or alkaline earth metals (suchas calcium or sodium ions) without significantloss of flame retardance.Only when the calcium or sodium ion pick-up exceeds this tolerance willa significant loss of fire retardance occur. This tolerance varies withthe weight of the fabric, its weave and type of finish, the kind ofproportion of phosphorus compound used, the kind and proportion oftitanium or other heavy metal used, etc. It is because of these manyvariables that it is best to determine the effective proportions ofheavy metal compound by preliminary empirical testing rather thanbya'ttempting to derive the needed proportions from a general formula orequation.

i In applying the heavy metal compound to the pretreated textilevsubstrate somewhat better metal utilization, better durability of thefinish and lower strength loss of the substratemay'be obtained with somesystems if the phosphorus compound is in the form of an ammonium or analkali metal salt, preferably the sodium salt, than if the phosphoruscompound present on the substrate has free acid groups, Moreparticularly, in applying the present invention, it has been foundespecially advantageous to w'ash'the cotton cloth or other textilesubstrate in a dilute sodium carbonate (soda ash) orcaustic sodasolution after it has, been treated with the phosphorus-containing flameretardant and before it istreated with the titanium salt or: otherheavyme'tal salt solution.

'A still "somewhat better metal utilization and better durability of thefinish is obtained if the textile substrate is steamed or boiled inwater after treatment with the phosphorus compound and prior toapplication of the heavy metal compound. Th application of the heavymetal compound solution to the phosphorus pretreated substrate isconveniently conducted at room temperature, e.g., between and 35 C.,although higher or vlower temperatures may be used.

- .After.the..metal..compound is applied to the textile ma,-

terial containing the phosphorus flame retardant, it is allowed" toreact for aperiodfof time and then the unreacted zchemicals are washedout. As noted above, the treatedtextile materialcontains from about 0.5to about 5, preferably from about- 0.8 to about 3, weight percentphosphorus.

The fabrics may washed in water with a little nonionic wetting agent.Basic materials may be added to the wash water if the fabric containsacidic materials to be neutralized-, Examples of basic.,materials that,can be used are soda ash, ammonium hydroxide, sodium siliof which isknown and described, for example, in U.S.

Pat. 2,979,374. The cotton fibers, and the like, are reacted with anaqueous solution of an alkali metal salt of chloromethylphosphonic acid,thereby producing a phosphonomethyl ether or cellulose.

Similarly, the flameproofed cellulosic textile material may be one whichhas been treated with an aqueous solution of cyanamide and phosphoricacid, as described, for example in U.S. Pat. 3,567,359, or withdicyandiamide and phosphoric acid, as described in U.S. Pat. 3,479,211,or with phosphoric acid and urea, as described in U.S. Pat. 3,253,881.

As the result of the treatment of the invention, the flame retardance ofthe textile material is improved and protected against ion exchange withother metal ions such as calcium and sodium such that the flameretardant properties are maintained through 30 to 50 or more launderingsin hard water.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples serve toillustrate the practice of the invention, but are not to be consideredas limiting:

EXAMPLE 1PART A Preparation of Phosphonomethylated Cotton Aflameproofing solution of the sodium salt of chloromethylphosphonic acidwas prepared as follows:

Percent by weight Chloromethylphosphonic acid 11.2 Sodium hydroxide 32.0Water 56.8

. the HCl formed. Usually the attachment of about 5% to 7% of thechloromethylphosphonic acid to the cellulose is sufficient to inhibitcombustion.

The treated cotton is washed in a 0.017% solution of non-ionicdetergent, such as Triton X-lOO (an ethoxylated nonyl phenol), rinsedand dried.

The treated fabric is .then soaked in a 2% HCl solution for 15 minutes,in order to convert the agent to the acid form, rinsed in deionizedwater and dried.

When tested by the AATCC Test Method 34-1969 (vertical flame test) thefabric exhibited a char length of 4% inches.

After the treated fabric was given a home laundering according to AATCC124-1969 (Machine Wash B at C.) and tumble drying, the fabric burned theentire length when tested.

EXAMPLE l-PART B Treatment of Phosphonomethylated Cotton The fabricprepared as described above in Part A is 7 padded with an aqueoussolution containing approximately 12.5% TiCL, by weight to an 85% wetpick-up. The fabric is then aged for minutes and is then washed in awashing machine with water containing 25 grams soda ash to removeacidity. The resulting product contains about 1.2% to 1.7% phosphorusand about 1.8% to 2.6% titanium, the atomic ratio of titanium tophosphorus being somewhat greater than 1:1.

The titanium tetrachloride treatment reaction can be represented by theequation:

The resulting fabric does not exhibit ion exchange properties towardhard water and retains its fire retardance for over 50 launderings. Whentested by AATCC 34-1969 the fabric exhibited a char length of 3 inches.After having been laundered and tumble dried 50 times according to AATCC124-1969, the fabric exhibited a char length of 4 inches.

EXAMPLE 2 Treatment of Phosphonomethylated Cotton Phosphonomethylatedcotton prepared as in Part A of Example 1 is padded to an 85 wet pick-upwith a treating bath having the composition:

Percent by weight Titanium tetrachloride 8.0 HCl 4.5 Water 87.5

Treatment with Ammonium Molybdate Phosphonomethylated cotton prepared asa Part A of Example 1 is padded to an 85 wet pick-up with a treatingbath having the composition:

Percent Ammonium molybdate 12 Water 88 The fabric is dried and cured ina circulating air oven for 10 minutes at 250 F. It is given an afterwashwith 0.01% Triton X-100 detergent in a washing machine. The fabricexhibits a char length of 3% inches when tested by AATCC 34-1969, thevertical flame test.

The fabric is laundered in water in which the hardness is raisedartificially to 300 p.p.m. After two such launderings, the char lengthof the fabric is still 3 inches.

EXAMPLE 4-P-ART A Diammonium Phosphate-Urea-Titanium TetrachlorideTreatment of Cotton Phosphate Treatment.-Cotton twill weighing about 8ounces per square yard is treated with a bath having the composition:

Percent by weight Diammonium phosphate 16.5 Urea -33 Triton X-100 0.1

EXAMPLE 4PART B Diammonium Phosphate-Urea-Titanium TetracholrideTreatment of Cotton Titanium Salt Treatment.The fabric treated asdescribed above in Part A is next padded through an aqueous solutioncontaining 21% TiCl with two nips and two dips, to a 72% wet pick-up andaged wet for 2 hours. It is then given another process wash with 0.1%Triton X-100 solution and 0.03% soda ash, rinsed and dried. The fabricnow contains about 3% titanium. The laundering durability of itsfiameproofing finish is determined by submitting representative samplesto flame tests and by determining their phosphorus and titanium contentafter a known number of laundering and tumble drying cycles. Somesamples were laundered at 120 F. and other samples at 140 F. The flametest results are shown below in Table I and the chemical analysisresults are shown in Table II.

Both the flame test data and the chemical analyses show that theinvention produces a flame retardant finish which is durable over 50 ormore laundering cycles. It has been observed in this work that this fireretardant finish often shows improved fire retardant properties afterextensive launderings. For example, certain fabrics will have shorterchar lengths after 30 to 50 launderings than after the first one to tenlaunderings. The cause for this is not known. It may be due to somethingpicked up by the fabric or lost by the fabric during laundering.

TABLE I [Laundering durability of Ti-urea-DAPcotton twill] SampleLaunder temperature 120 F 120 F. 140 F. 140 F Char A. G1 Char A. (3.Char A.G. Char ILG. (in.) (sec.) (in.) (sec.) (in.) (sec.) (in.) (sec.)

3-sec. vertical flame test:

L-l-T.D. (cycles):

3.25 19 3.75 24 3.00 135 i 3.25 g V B These samples were testi ed inbone-dry condition according to D0 CFB:371. The other samples wereconditioned at 65% R.H. at 70 b Afterglow v Laundering and tumbledrying.

TABLE II [Analysis of Ti-urea-DAP-eotton twill after laundering] LaunderAfter L+T.D. mp Analysis Sample F. percent 15 30 50 30-1 120 P 1.821.86 1. 83 1.58 1.56 Ti 3.42 3.10 2.31 v 2.97 3.04

30-3 140 P 1. 94 1.73 1.76 1.32 1. 47 Ti 3.05 2. 90 2. 69 2. 96 2. 81

30-4 140 P 1.95 1.72 1.77 1.38 1.39 Ti 3. 39 3. 17 3.12 2. 96 3.05

EXAMPLE 5 Treatment with TiCl (OH) Two moles (384 grams) of TiCl aredissolved in 900 grams of water. Four moles of NaOH (320 grams of a 50%solution) are added with stirring and cooling to the Tifll... (Causticcan be added carefully to TiCl without precipitation occurring if nomore than 3 moles of caustic are added to one mole of TiCl When 4 molesof NaOH are added to 2 moles of TiCl the solution contains 2 moles ofTiCl (OH) and 4 moles of NaCl.

Cotton twill is treated with diammonium phosphate and urea as in Example4Part A. This treated twill is boiled in water for minutes and dried.The dried, treated twill is padded with the TiCl (OH) treating bath to a90% wet pick-up. The wet fabric is aged one hour and then given aneutralizing wash in the washing machine with 10 grams of Triton X-100detergent and 50 grams of concentrated ammonium hydroxide. The fabric isrinsed, dried and subjected to laundering and testing for fireretardance. The fabric contains about 2% phosphorus.

When tested by AATCC 34-1969, the fabric has a char length of 4 inchesafter 50 launderings and tumble drymgs.

EXAMPLE 6 Example 4 is repeated except that the phosphate treatment bathcontains 8% by weight diammonium phosphate, 16% by weight urea and 0.1%by weight Triton X- 100. The treated fabric contains about 1.2% byweight phosphorus.

' When tested by AATCC 34-1969, the fabric shows acceptable flameretardant properties.

EXAMPLE 7 Unmercerized fiannelette weighing 3.25 oz./ sq. yd. is paddedthrough the phosphate treatment bath of Example 6 with two dips and twonips to a wet pick-up of 95%. The fabric is dried 5 minutes at 250 F.and cured 7 minutes at 330 F., afterwashed in water with a little sodaash and Triton X-100, rinsed and dried.

This treated fabric is padded with an aqueous solution of 25% TiCl to awet pick-up of 140%. The wet fabric is aged for 60 minutes, neutralizedin a washing machine with ammonia water, rinsed and dried. The fireretardance is tested by DOC FF 3-71 (vertical flame test) initially andafter laundering in a sodium tripolyphosphate-containing detergent andtumble drying.

The results of this testing are:

No. of Launderings Char Length (inches) 0 Burned entire length. 1 9.5.

The fire retardance of these lightweight samples increases withincreased launderings in detergent which contains sodiumtripolyphosphate. Other lightweight samples such as broadcloth (3.25oz./sq. yd. fabric weight) which exhibit suitable fire retardance aftertreatment with the process of the present invention also displayincreased fire retardance with launderings or process washeswith sodiumtripolyphosphate. 1

EXAMPLE 8 Unmercerized flannelette (3.25 oz./sq. yd.) is treated in thesame way as in Example 7 except that after the fabric is neutralized inammonia water, it is washed for 5 minutes in 1% sodium tripolyphosphate,rinsed and dried.

Washing the treated fabric with sodium tripolyphosphate improves theinitial fire retardance.

EXAMPLE 9 Mercerized flannelette weighing 3.25 oz./sq. yd. is treatedthe same as the unmercerized fiannelette in Example 8. This fabric islaundered and tested for fire retardance.

No. of Launderings Char Length (inches) 0 5.0 5 4.75

Comparison of Examples 8 and 9 shows that the treatment is effective oneither mercerized or unmercerized fabric.

EXAMPLE 10 A sample of 4.1 oz./sq. yd. flannelette is padded through thephosphate treatment bath of Example 6 with two dips and two nips to awet pick-up of The fabric is dried 5 minutes at 250 F. and cured sevenminutes at 330 F., after washed in water with a little soda ash andTriton X-100, rinsed and dried.

The treated fabric is padded through 12.5% TiCL; with two dips and twonips and immediately neutralized in 15% NH in a beaker. The fabric isrinsed and given a process wash in 1% sodium tripolyphosphate.

Tllie fabric is laundered and tested with the following resu ts:

No. of launderings Char length (inches) After-Treatment With OtherMetals Another batch of cotton twill is treated with the diammoniumphosphate-urea solution in the same manner as described in Example 4PartA (except as indicated), but instead of the treatment with titanium saltsolution, is then treated with solutions of other metal salts. The metalsalts used and the fire retardance results obtained are shown in TableIII below. The cotton twill has a fabric weight of 8 oz./ sq. yd.

The results show that with the exception of zinc chloride, zirconiumoxychloride, aluminum chloride, and the mixed titanium chloride-antimonyoxide, all the other salt solutions tested have produced a verynoticeable improvement in the durability of the fire retardant finish.

It should be understood that the foregoing description TABLE II CharA.G. Char A.G. Char Char Char A.G. Metal salt solution (in.) (sec.)(in.) (sec.) (in.) (see.) (in.) (sec (in.) (500.)

None control 3. 05 0 a BEL 0- 32% 31 101402 4. 00 10 4. 00 10 32% SnCh,10% HCl. 3. 75 7 3. 00 16 22% ZrOCh 4. 7o 2 BEL 22% ZIOClz, 10% HC1 4.504 BEL 35% 81101 10% HCl. 2. 7o 14 2. 50 %111012, 10% I101. BEL 0 BEL 20%CrClg, 10% HO]. 5. 205 6. 25 20% A1011. 10% HO]. BEL 0 BEL 16.7% AlCl;BEL 0 BEL 18% CuClz 5. 00 95 4. 25 23% 5.00 150 (i. 00 12% 3.0

1 S m les conditioned 18 hours at 65 RH. and 70 F. prior to testing. 2Sample is unmercerized flannelette t ieated with 16% urea and 8%diammomom phosphate as in Example 6. After neutralization, the treatedfabric was given an aiterwash in 10% sodium tripolyphosphate.

3 B EL"=burned entire length.

What is claimed is:

1. In combination with a process wherein flame retardant properties areimparted to a web of cellulosic or protein fiber material by treatmentthereof with a phosphorus-containing flame-proofing agent which isaflixed to the fiber in an amount of from about 0.5 to about 5 percentphosphorus by weight of the fiber and which has ion exchange capability,wherein the improvement comprises applying to said treated web asolution of a soluble compound of a metal belonging to Group I-B, IV-A,IV-B, V-A, V-B, VI-B, VII-B and VIII of the Periodic Table, and dryingthe Web.

2. The process of Claim 1 in which the metal compound is titanium salt.

3. The process of Claim 1 in which the soluble metal compound is a saltof Cr 4. The process of Claim 1 in which the metal compound is acompound of Gu Fe Sn Sb or Me.

5. The process of Claim 1 in which the material is a cellulosic textilematerial having a fabric weight of at least about 5 ounces per squareyard.

6. The process of Claim 5 in which the material is cotton and the metalcompound is a titanium chloride corresponding to the formula TiCl (OH).;in which n is an integer in the range from 1 to 4.

7. The process of Claim 5 in which the treated material isphosphonomethylated cotton.

8. The process of Claim 5 in which the material is a cotton fabric towhich an aqueous solution including an organic base and a phosphorusacid compound is applied and cured and thereafter treated with saidmetal compound.

9. The process of Claim 8 in which the organic base is urea.

10. The process of Claim 9 in which the phosphorus acid compound isincluded in the solution as diammonium phosphate or as orthophosphoricacid.

11. A process according to Claim 10 wherein the cotton is treated withan aqueous solution of a sodium carbonate or hydroxide after applicationof the phosphorous acid compouund and before application thereto of thesoluble metal compound.

12. A process according to Claim 11 wherein the cotton is cured byboiling in water or steaming after application of the phosphorus acidcompound and treatment with sodium base and before application theretoof the soluble metal compound.

13. The process of Claim 2 in which the atomic ratio of metal ion tophosphorus present in the treated textile material is between about 0.5:1 and about 5:1.

14. The process of Claim 1 wherein the treated web is washed in a sodiumtripolyphosphate-containing solution.

15. The process of improving and. prolonging the flame retardantproperties of 'phosphonomethylated cotton which comprises treating saidcotton with a titanium chl0- ride, the atomic ratio of titanium tophosphorus being approximately 1:1.

16. In a process for imparting durable flame retardan properties to acotton textile material in which (a) an aqueous solution containingdiammonium phosphate and urea is applied to said material, therebyaffixing to said material from 0.5 to 5.0 percent phosphorus based onthe weight of the cototou and converting cellulose in the cotton into anester derivative corresponding to the formula References Cited UNITEDSTATES PATENTS Lewis et al. 117-l38 2,658,000 11/1953 Sullivan et al.117136 X 2,668,780 2/1954 Panik et al. 11762.1 2,728,680 12/1955 Duane'117138 X 2,979,374 4/1961 Drake et al. 117136 X 3,253,881 5/1966Donahue 117136 X WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS,Assistant Examiner U.S. Cl. X.R.

